A preparing device for preparing an aqueous beverage is, for example, a device for preparing instant beverages. An example thereof is known from WO 03/068039. With such instant beverage-preparing devices, liquid, such as hot water, is mixed in a mixing device with an instant ingredient, in the case of WO 03/068039 an instant powder. Referring to said example, WO 03/068039, such a mixing device has a preparation chamber in the form of a mixing chamber containing a rotor. The mixing chamber is usually subdivided into an inlet chamber and a rotor chamber. Instant powder is delivered to the mixing chamber by means of an ingredient-dispensing system. This system comprises an access opening at the top of the inlet chamber via which portions of instant powder are delivered to the inlet chamber. The inlet chamber has furthermore an inlet nozzle by means of which hot water is supplied by a supply line. Using a round inlet chamber and a radially oriented inlet, a mixing action is achieved in the inlet chamber due to the liquid making a circular movement. From the inlet chamber, the liquid with the instant powder passes to the rotor chamber where the rotor is situated. The rotor is usually arranged in such a manner that it rotates about a horizontal axis of rotation, as is also the case in WO 03/068039. As a result thereof, a pipe bend is usually provided between the inlet chamber and the rotor chamber. The rotor may perform various functions, optionally in combination, and may, partly for this reason, have various forms. One function is to improve the mixing. Another function is foaming up the beverage by mixing in air or by another way. Yet another function is a conveying function. Furthermore, an outflow path in the form of an outlet duct is connected to the mixing chamber, usually to the rotor chamber near the rotor, in order to discharge the mixture produced, generally into a container, such as a beaker, mug, cup or pot, from which the beverage can be drunk or poured. The outlet is generally horizontally oriented and has a discharge part at the end having an outflow nozzle which is directed downwards by means of a bend, also referred to as an outflow opening.
Another type of device for preparing an aqueous beverage is, for example, the type in which water is passed through a cartridge containing beverage ingredient or a bed of beverage ingredient. Consideration may be given here, for example, to espresso machines for preparing espresso coffee or filter coffee machines in which coffee powder is placed into a funnel-shaped paper filter and the water flows down through the bed on account of the force of gravity. Referring to systems which are currently commercially available, the following may be mentioned by way of example: the Tassimo® system by Kraft® which uses cartridges containing liquid concentrate; the Nespresso® system by Nestlé® which uses closed aluminium cups containing ground coffee powder; the systems operating at a pressure of 1-2.5 bar by Philips®/Sara Lee® (the Senseo® system), Bosch (Augusto®), Severin®, all of which use cartridges consisting of two layers of filter paper which are sealed together at the edge and which contain coffee powder or fannings of tea leaves. With devices of this type, a container is provided for accommodating the cartridge. This container or the cartridge itself delimits the preparation chamber. The ingredient-dispensing system in this case is usually provided in the preparation chamber. In the case of a bed of ground coffee, the ingredient-dispensing system may comprise, for example, a filter, such as a filter made from filter paper, as well as the bed of ground coffee itself. Furthermore, with devices of this type, it is known to subject the liquid flowing through the outflow path to further processing steps, such as foaming, or to add further ingredients to this path.
Mechanical parts, such as bearing bushes and toothed wheels, which comprise a mixture of polyoxymethylene, polytetrafluoroethylene and calcium carbonate are known from DE A 4.445.316. These parts have improved sliding properties and show little wear. The parts preferably contain 50-98 parts by weight of polyoxymethylene, 1-25 parts by weight of polytetrafluoroethylene and 1-25 parts by weight of calcium carbonate.
WO 2006/014393 discloses an aqueous coating composition, which comprises tetrafluoroethylene polymer particles and particles of a non-fluorinated polymer. The coating composition can be applied to a substrate such as glass, metal or stainless steel and provides coatings which are able to resist adhesion, wear and the effects of hot salt water very well.
US 2004/107841 discloses a device for preparing a coffee drink having an appealing creme layer comprises a container for receiving flavour-containing materials and allowing it to interact with pressurised hot water to produce a coffee drink.
The instant beverage-preparing devices known for preparing instant beverages have various shortcomings, that is to say there are various points which can be improved upon. One of the main shortcomings is the fact that water and/or moisture and/or instant ingredient, such as instant powder, is deposited on certain parts of the mixing device which is disadvantageous in connection with hygiene. As a result thereof, such mixing devices and the parts thereof have to be cleaned regularly. In this case, it would be advantageous if the frequency with which the mixing device or the parts thereof have to be cleaned could be reduced.
These disadvantages which occur with instant beverage-preparing devices also occur in the case of the above-described devices of the type where water is passed through a cartridge containing beverage ingredient or a bed of beverage ingredient. In this case, too, water and/or moisture and/or beverage ingredient is deposited.
Such deposits not only necessitate regular cleaning, but also prevent the use of the same parts for the preparation of different beverages. In order to prevent flavour contamination (that is to say transference of flavour constituents from one beverage to the other beverage), measures have to be taken, such as rinsing prior to preparing a different type of beverage.
It is therefore an object of the present invention to provide a preparing device for preparing an aqueous beverage by means of a beverage ingredient, in which deposits on parts through which the aqueous beverage flows or parts coming into contact with the aqueous beverage are prevented.
Another object of the present invention is to improve the hygienic conditions under which the aqueous beverage is prepared.